I'm leaning towards the LFA. It looks like a much more special car and it is a much more special car in its construction. I prefer the long front, short rear deck proportion of a true 2-seater front-engined sports car, but have to admit the GT-R's rear seats are a huge bonus. Though it's not really a part of this discussion, the price of the LFA can be rationalized.
Will be quite interesting to read a head-to-head comparo. Many of the initial drive impressions so far are contradictory in regards to the steering feel and brakes; some think the LFA delivers strongly in these areas, while others, driving what should be identically prepared cars on the very same roads and track, think it feels distant.
All pretty much agree that the engine is a masterpiece, with amazing revvability; but they almost all agree that the single-clutch transmission that helps make this possible takes a back seat to modern DCT's. This, for me, is another area where the LFA can't quite make the knock-out blow to the GT-R. From what I can tell, the LFA should be the better track car (and will probably last longer under sustained lapping), the GT-R the more competent road car.